U.S. patent application number 09/545333 was filed with the patent office on 2002-11-28 for film for thermal laminate.
Invention is credited to Yamashita, Takashi.
Application Number | 20020177005 09/545333 |
Document ID | / |
Family ID | 14289791 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020177005 |
Kind Code |
A1 |
Yamashita, Takashi |
November 28, 2002 |
Film for thermal laminate
Abstract
Disclosed is a film comprising a thermoplastic resin film, a
first layer comprising a resin (A), and a second layer comprising a
resin (B), in this order, wherein the resin (A) is an ethylene
resin having a density of 0.900 to 0.960 g/cm.sup.3 and an MFR of 1
to 100 g/10 minutes, and the resin (B) is a straight-chain
ethylene-a-olefin copolymer having a density of 0.870 to 0.910
g/cm.sup.3 and an MFR of 1 to 100 g/10 minutes, the straight-chain
ethylene-a-olefin copolymer being a copolymer of ethylene with at
least one .alpha.-olefin having 3 to 12 carbon atoms.
Inventors: |
Yamashita, Takashi; (Mie,
JP) |
Correspondence
Address: |
Oblon, Spivak, McClelland,
Maier & Neustadt, P.C.
Fourth Floor
1755 Jeferson Davis Highway
Arlington
VA
22202
US
|
Family ID: |
14289791 |
Appl. No.: |
09/545333 |
Filed: |
April 7, 2000 |
Current U.S.
Class: |
428/516 ;
428/218 |
Current CPC
Class: |
B32B 37/153 20130101;
Y10T 428/24992 20150115; B32B 27/08 20130101; B32B 2323/046
20130101; Y10T 428/31913 20150401; B32B 27/32 20130101; C08L
23/0815 20130101; B41M 7/0027 20130101; B32B 27/10 20130101 |
Class at
Publication: |
428/516 ;
428/218 |
International
Class: |
B32B 027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 1999 |
JP |
P. HEI. 11-101030 |
Claims
What is claimed is:
1. A film, which comprises a thermoplastic resin film, a first
layer comprising a resin (A), and a second layer comprising a resin
(B), in this order, wherein the resin (A) is an ethylene resin
having a density of 0.900 to 0.960 g/cm.sup.3 and an MFR of 1 to
100 g/10 minutes, and the resin (B) is a straight-chain
ethylene-a-olefin copolymer having a density of 0.870 to 0.910
g/cm.sup.3 and an MFR of 1 to 100 g/10 minutes, the straight-chain
ethylene-.alpha.-olefin copolymer being a copolymer of ethylene
with at least one .alpha.-olefin having 3 to 12 carbon atoms.
2. The film according to claim 1, which is for thermal
laminate.
3. The film according to claim 1, wherein the straight-chain
ethylene-.alpha.-olefin copolymer in the second layer is eluted at
a temperature of 80.degree. C. or lower as determined by
temperature rising elution fractionation (TREF) method in an amount
of 90% by weight or more based on the total weight of the
copolymer.
4. The film according to claim 1, wherein the straight-chain
ethylene-.alpha.-olefin copolymer in the second layer is
polymerized using a metallocene compound as a polymerization
catalyst.
5. The film according to claim 1, wherein the straight-chain
ethylene-a-olefin copolymer is an ethylene/propylene copolymer, an
ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an
ethylene/1-octene copolymer, an ethylene/propylene/1-butene
copolymer, or an ethylene/propylene/1-hexene copolymer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a film for thermal laminate
which is adapted to be heat-bonded to the surface of a printing
paper or the like to protect the surface of the printed matter.
BACKGROUND OF THE INVENTION
[0002] It is widely practiced to laminate a film on a printing
paper for the purpose of protecting the surface of the printing
paper, rendering the printing paper water-resistant or
oil-resistant or improving the surface gloss of the printing paper.
The film for thermal laminate to be used for these purposes usually
comprises a stretched polypropylene film as a substrate film and a
solvent type ethylene-vinyl acetate copolymer-based adhesive as an
adhesive therefor. However, since the foregoing method involving
the use of a solvent type adhesive requires the handling of a
solvent, particular attention should be given to recovery of
solvent or working atmosphere. Further, the foregoing method
usually requires the use of a hardener, it is necessary to take
into account pot life.
[0003] An example of the method for the preparation of a laminate
film free from organic solvent or adhesive is a method which
comprises laminating a biaxially-stretched polypropylene laminate
film provided with a heat-sensitive adhesive layer made of a
mixture of two or more of ethylene-alkylester copolymers and
ethylene-vinyl acetate copolymers, with a printing paper only by
heat-bonding process in such an arrangement that the heat-sensitive
adhesive surface of the laminate film and the adhesive surface of
the printing paper were opposed to each other (JP-A-56-42652 (The
term "JP-A" as used herein means an "unexamined published Japanese
patent application"), JP-B-4-2431 (The term "JP-B" as used herein
means an "examined Japanese patent application"), JP-A-3-73341)
However, since the heat-sensitive adhesive layer comprises as an
ethylene copolymer resin one having a maximized content of
functional monomer to meet the requirement for ease adhesion to the
printed surface, the resulting laminated film exhibits deteriorated
lubricating properties and blocking resistance. Thus, the Laminated
film can be less easily released from the roll or can be wrinkled
during production. Further, when the laminated film is carried or
stored in a wound form, the substrate and the ethylene copolymer
resin which have been superimposed on each other are stuck to each
other. Thus, when the laminated film is unwound before being
laminated on the printed surface, the resulting raised lamination
tension causes the laminated film to be elongated or broken.
[0004] A further example of the foregoing lamination method is one
which comprises laminating a laminated film, in which a resin
containing an ethylene resin in a straight-chain
ethylene-.alpha.-olefin copolymer obtained in the presence of a
metallocene compound as a catalyst is laminated on a substrate, on
a printing paper, only by heat-bonding process, so that a thermal
laminate product is produced (JP-A-7-117197). However, this
laminated film exhibits a deteriorated cuttability during print
lamination. Further, since this method involves the use of a single
straight-chain ethylene-.alpha.-olefin copolymer, surging occurs
during extrusion lamination, making it impossible to form film.
SUMMARY OF THE INVENTION
[0005] It is therefore an object of the invention to provide a film
for thermal laminate which is prepared by co-extruding two kinds of
resins into two layers so that no surging occurs during extrusion
lamination, a stabilized film can be formed, print lamination can
be effected at a low temperature, the resulting thermal laminate
undergoes no discoloration of printing ink or no curling, the
laminated film exhibits an improved cuttability during print
lamination, no odor of solvent is generated during print
lamination, no apparatus for removing and recovering the solvent is
required, there is no necessity of taking into account pot life, no
wrinkling occurs during the production of film, and the laminated
film undergoes no elongation or breakage during print
lamination.
[0006] The foregoing object of the present invention will become
apparent from the following detailed description and examples.
[0007] The inventors made extensive studies of solution to the
foregoing problems. As a result, it was found that by laminating a
specific ethylene resin on one side of a thermoplastic resin film
substrate and then heat-bonding a specific straight-chain
ethylene-.alpha.-olefin copolymer layer to the ethylene resin layer
in such an arrangement that it comes in contact with the printed
surface of a printed matter, a stable film can be formed which can
be laminated on the printed surface of a printed matter at a low
temperature, can prevent the printed matter from being curled, can
be cut more easily during lamination and can be prevented from
undergoing surging during extrusion lamination. Thus, the present
invention has been worked out.
[0008] The present invention provides a film for thermal laminate
comprising a resin layer (A) provided in contact with one side of a
thermoplastic resin film substrate and (B) a resin layer (B)
laminated thereon:
[0009] Resin (A): Ethylene resin having a density of from 0.900 to
0.960 g/cm.sup.3 and MFR of from 1 to 100 g/10 minutes; and
[0010] Resin (B): Straight-chain ethylene-.alpha.-olefin copolymer
having a density of from 0.870 to 0.910 g/cm.sup.3 and MFR of from
1 to 100 g/10 minutes obtained by the copolymerization of ethylene
with an a-olefin having 3 to 12 carbon atoms.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention will be further described
hereinafter.
[0012] 1. Thermoplastic Resin Film Substrate of Laminating Film
[0013] Examples of the thermoplastic resin film substrate to be
used in the laminated film which is the film for thermal laminate
of the invention include stretched or unstretched film of
thermoplastic resin such as polypropylene, polyethylene,
polyethylene terephthalate, polyvinyl chloride and polystyrene. The
thickness of the substrate film is preferably from 6 to 100 .mu.m,
more preferably from 7 to 40 .mu.m. The thermoplastic resin film
substrate may comprise a lubricant, an anti-blocking agent, a
stabilizer, an oxidation inhibitor, an antistatic agent, an
anti-fogging agent, a colorant and other additives incorporated
therein.
[0014] 2. Adhesive Resin Layer
[0015] The resin layer to be laminated on the surface of the
foregoing thermoplastic resin film substrate comprises the
following ethylene resin (A) layer and straight-chain
ethylene-.alpha.-olefin copolymer (B) layer laminated thereon:
[0016] (A) Ethylene Resin
[0017] The ethylene resin to be used herein exhibits a density of
from 0.900 to 0.960 g/cm.sup.3, preferably from 0.905 to 0.950
g/cm.sup.3, particularly from 0.915 to 0.945 g/cm.sup.3 (as
determined by process A according to JIS K7112). When the density
of the ethylene resin falls below 0.900 g/cm.sup.3, the resulting
laminating film exhibits a deteriorated cuttability during
lamination. On the contrary, when the density of the ethylene resin
exceeds 0.960 g/cm.sup.3, the adhesion between the ethylene resin
(A) layer and the resin (B) layer described later is deteriorated.
Further, the external appearance of thermal laminate is marred
(obscured). The thermal laminate can also be easily curled.
[0018] The ethylene resin exhibits MFR of from 1 to 100 g/10
minutes, preferably from 2 to 80 g/10 minutes, as determined under
Condition 4 according to JIS K7210. When MFR of the ethylene resin
falls outside the above defined range, the resulting ethylene resin
exhibits too high or low a melt viscosity and hence a deteriorated
formability.
[0019] Examples of the ethylene resin employable herein include the
following compounds:
[0020] (a) Branched high pressure process low density polyethylene,
and copolymer resin obtained by the copolymerization of ethylene
with a monomer copolymerizable therewith, e.g., vinyl acetate,
acrylic acid, methyl acrylate, ethyl acrylate and methacryl
methacrylate. Specific examples of these resins include
ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer,
ethylene-methyl acrylate copolymer, and ethylene-ethyl acrylate
copolymer. These resins may be used singly or in combination of two
or more thereof.
[0021] (b) A mixture of low pressure process high density
polyethylene with 1% by weight or more of at least one of the
resins listed in the group (a).
[0022] (c) A mixture of a straight-chain ethylene-.alpha.-olefin
copolymer obtained by the copolymerization of ethylene with a
C.sub.4-12 .alpha.-olefin (a-olefin having 4 to 12 carbon atoms)
with 1% by weight or more of at least one of the resins listed in
the group (a).
[0023] (d) A mixture of a straight-chain ethylene-.alpha.-olefin
copolymer obtained by the copolymerization of ethylene with a
C.sub.4-12 .alpha.-olefin in the presence of a metallocene compound
as a polymerization catalyst with 1% by weight or more of at least
one of the resins listed in the group (a).
[0024] (B) Straight-Chain Ethylene-.alpha.-Olefin Copolymer
[0025] The straight-chain ethylene-.alpha.-olefin copolymer to be
used as the resin layer (B) of the invention is a copolymer
obtained by the copolymerization of ethylene with at least one
C.sub.3-12 .alpha.-olefin.
[0026] Specific examples of such a copolymer include bicopolymer
obtained by the copolymerization of ethylene with one C.sub.3-12
.alpha.-olefin and tercopolymer obtained by the copolymerization of
ethylene with two C.sub.31-2 .alpha.-olefins.
[0027] Specific examples of the C.sub.3-12 .alpha.-olefin include
propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 1-decene, and
1-dodecene. These C.sub.3-12 a-olefins may be used singly or in
combination.
[0028] Preferred examples of the straight-chain
ethylene-.alpha.-olefin copolymer include ethylene-propylene
copolymer, ethylene-1-butene copolymer, ethylene-l-hexene
copolymer, ethylene-1-octene copolymer, ethylene-propylene-1-butene
copolymer, and ethylene-propylene-1-hexene copolymer.
[0029] The straight-chain ethylene-a-olefin copolymer exhibits a
density of from 0.870 to 0.910 g/cm.sup.3, preferably from 0.875 to
0. 900 g/cm.sup.3, as determined by process A according to JIS
K7112. When the density of the straight-chain
ethylene-.alpha.-olefin copolymer falls below 0. 870 g/cm.sup.3,
the resulting straight-chain ethylene-.alpha.-olefin copolymer
exhibits a deteriorated formability and a deteriorated blocking
resistance that can cause the laminating film to be elongated or
broken during print lamination. On the contrary, when the density
of the straight-chain ethylene-.alpha.-olefin copolymer exceeds
0.910 g/cm.sup.3, the resulting laminating film exhibits a
deteriorated adhesion to the printed surface of the printed matter
and mars the external appearance of thermal laminate (obscured
image)
[0030] The straight-chain ethylene-.alpha.-olefin copolymer
exhibits MFR of from 1 to 100 g/10 minutes, preferably from 2 to 80
g/10 minutes, as determined under Condition 4 according to JIS
K7210. When MFR of the ethylene resin falls outside the above
defined range, the resulting ethylene resin exhibits too high or
low a melt viscosity and hence a deteriorated formability. On the
contrary, when MFR of the ethylene resin falls below 1 g/10
minutes, the external appearance of thermal laminate is marred
(obscured).
[0031] The straight-chain ethylene-.alpha.-olefin copolymer to be
used herein can be prepared by the polymerization of the foregoing
monomers in the presence of a known titanium-based catalyst or
metallocene catalyst. The straight-chain ethylene-.alpha.-olefin
copolymer is preferably a copolymer prepared by high pressure ion
polymerization, gas phase polymerization or solution polymerization
in the presence of, as a polymerization catalyst, a metallocene
compound, particularly a metallocene catalyst having the following
physical properties.
[0032] The straight-chain ethylene-.alpha.-olefin copolymer is
preferably eluted at a temperature of 80.degree. C. or lower as
determined by temperature rising elution fractionation (TREF)
method in an amount of 90% by weight or more based on the total
weight of the copolymer.
[0033] The measurement of the amount eluted by TREF (temperature
rising elution fractionation) is carried out according to the
principle described in "Journal of Applied Polymer Science", Vol.
26, pp. 4,217-4,231, 1981, and "Koubunshi Ronbunshu (Theses of High
Molecular Compounds)", 2P1C09, 1985, in the following manner.
[0034] In some detail, the polymer to be measured is completely
dissolved in a solvent. Thereafter, the solution is cooled so that
a thin polymer layer is formed on the surface of an inert carrier.
The polymer layer thus formed comprises an inner layer (layer close
to the surface of the inert carrier) made of a polymer which can be
easily crystallized and a surface layer made of a polymer which can
be hardly crystallized. When the ambient temperature is raised
continuously or stepwise, the polymer layer undergoes elution
beginning with the amorphous portion in the polymer composition to
be measured, i.e., portion having many short-chain branches, in the
low temperature stage. When the ambient temperature gradually
rises, the degree of branching of the polymer portion thus eluted
decreases. Eventually, a straight-chain polymer portion free of
branches is eluted. Thus, measurement is terminated. The
concentration of the component eluted at the various temperatures
is detected. The graph made by plotting the amount eluted vs. the
elution temperature gives the composition distribution of
polymer.
[0035] As the straight-chain ethylene-.alpha.-olefin copolymer
there may be also used one obtained by graft polymerization of
maleic anhydride, styrene or the like.
[0036] The straight-chain ethylene-.alpha.-olefin copolymer may
further comprise a lubricant, an anti-blocking agent, a stabilizer,
an antistatic agent, an anti-fogging agent, a colorant, a low
molecular polymer and other various additives incorporated there as
necessary.
[0037] 3. Thickness of Adhesive Resin Layer
[0038] Referring to the thickness of the foregoing adhesive resin
layer, the sum of the thickness of the resin layer (A) and the
resin layer (B) is 6 .mu.m or more, preferably from 7 to 80 .mu.m.
The ratio of the thickness of the resin layer (A) to the resin
layer (B) is not limited. In practice, however, it is preferably
from 5:1 to 1:1.
[0039] 4. Film for Thermal Laminate
[0040] The film for thermal laminate according to the invention is
obtained by laminating a resin layer (A) on one side of a
thermoplastic film substrate, and then laminating a resin layer (B)
on the resin layer (A). Examples of the method for the preparation
of the film for thermal laminate according to the invention include
tandem extrusion coating method which comprises laminating a resin
layer (A) on the substrate, and then laminating a resin layer (B)
on the resin layer (A); sandwich lamination method which comprises
laminating a resin layer (B) with a molten resin layer (A); method
which comprises dry-laminating a two-layer film consisting of
resins (A) and (B); and two-layer ((A) and (B)) melt co-extrusion
coating method. Preferred among these lamination methods is
two-layer co-extrusion lamination method, which allows the
formation of a thin film at a high speed. In the case where the
two-layer co-extrusion lamination method is used, the working
temperature is from 150.degree. C. to 300.degree. C., preferably
from 200.degree. C. to 280.degree. C. The interface of the
thermoplastic resin film substrate with the resin layer (A) is
preferably subjected to ozone treatment.
[0041] In the case where the resins (A) and (B) are subjected to
two-layer melt co-extrusion lamination, the thermoplastic resin
film substrate is preferably subjected to surface treatment such as
corona treatment or coated with an anchor coat.
[0042] The film for thermal laminate thus obtained is then
preferably subjected to oxidation such as corona treatment and
ozone treatment on the surface of the resin layer (B) to improve
its adhesion to the printed surface of the printed matter. In
particular, corona treatment is the most simple and effective.
[0043] The present invention will be further described in the
following examples, but the present invention should not be
construed as being limited thereto. The characteristics of the
laminating film used in the examples, the method for the evaluation
of the characteristics of the thermal laminate in the examples, and
the resins used in the examples are as follows.
[0044] 1. Evaluation Method
[0045] (1) Workability:
[0046] The molten resin which has been extruded through a T-die at
a take-off speed of 200 m/min. to a lamination thickness (total
thickness if there are two layers) of 15 .mu.m is observed for the
occurrence of surging (thickness change of .+-.5 .mu.m or more in
the flowing direction). For the evaluation of surging, the
following criterion is used.
[0047] Good: No surging occurs
[0048] Poor: Surging occurs, making it difficult to form film
[0049] (2) Blocking Resistance:
[0050] A biaxially stretched film having a width of 21 cm and a
length of 29 cm and a laminating film having the same size are
superimposed on each other in such an arrangement that the surface
of the biaxially stretched film is opposed to the corona-treated
surface of the laminating film. The laminate is then allowed to
stand in a 60.degree. C. oven under a load of 0.05 kg/cm.sup.2 over
an area having a width of 15 cm and a length of 20 cm for 24 hours.
The laminated film is then cut to an area of 10 cm.sup.2 (width: 2
cm; length: 5 cm) to be subjected to peeling. The load required to
peel the films off from each other at a pulling rate of 500
mm/minute by a tensile testing machine is then measured. The
smaller the load value thus measured is, the better is the blocking
resistance. For the evaluation of blocking resistance, the
following criterion is used.
[0051] .times.: Peeling load of 2 kg/10 cm.sup.2 or more (laminated
film breaks)
[0052] .DELTA.: Peeling load of 1.5 to less than 2 kg/10
cm.sup.2(laminated film is fully elongated)
[0053] .smallcircle.: Peeling load of 1.0 to less than 1.5 kg
(laminated film is elongated but recovered)
[0054] .circleincircle.: Peeling load of less than 1.0 kg
[0055] (3) Gloss and Obscured Image:
[0056] For the measurement of gloss, a Type UGV-5DP glossmeter
produced by Suga Test Instruments Co., Ltd. is used. In some
detail, the printed area of the thermal laminate is measured at an
angle of 20 degrees. For the measurement of obscured image
(adhesion between the printing paper and the laminating resin), the
external appearance of the printed matter is visually observed for
obscured image. For the evaluation of obscured image, the following
criterion is used.
[0057] .smallcircle.: No residual air, sharp printing color
[0058] .DELTA.: Air remains on the printing color in stripes or
spots
[0059] .times.: Air remains on the printing color in the form of
belt, obscuring the printing color
[0060] (4) Adhesive Strength:
[0061] The thermal laminate is cut to specimens having a width of
25 mm and a length of 100 mm. The laminating films are then peeled
off from each other over a length of 50 mm. The tensile strength
required to peel the laminating films off from each other at an
angle of 180 degrees at a pulling rate of 300 mm/minutes by a
tensile testing machine produced by a tensile testing machine
produced by Shimadzu Corp. is then measured.
[0062] (5) Tunneling:
[0063] For the measurement of tunneling, 100 .mu.l of gas oil is
dropped through a syringe onto the thermal laminate on the side
thereof free of printing paper. The specimen is then allowed to
stand at a temperature of 23.degree. C. and a humidity of 50% for
24 hours. The resulting change of the surface conditions of the
laminated film is then observed. For the evaluation of tunneling,
the following criterion is used.
[0064] .circleincircle.: No problems of adhesive strength and
external appearance
[0065] .smallcircle.: Slight drop of adhesive strength, but no
change of of external appearance (acceptable level)
[0066] .DELTA.: Slightly obscured image
[0067] .times.: Tunneling occurs explicitly
[0068] (6) Elmendorf Tear Strength:
[0069] The thermal laminate is subjected to tear test for plastic
film and sheet according to Elmendorf tear testing method (process
B according to JIS K7128).
[0070] (7) TREF:
[0071] For TREF (temperature rising elution fractionation), the
polymer is dissolved at a high temperature, and then cooled so that
a thin polymer layer is formed on the surface of an inactive
carrier. The ambient temperature is then raised continuously or
stepwise. The component thus eluted is recovered, and continuously
detected for concentration. The graph obtained by plotting the
amount eluted vs. the elution temperature (elution curve) is then
observed for peaks from which the composition distribution of
polymer is then determined.
[0072] The foregoing elution curve is determined as follows. For
the measurement of elution, a Type CFC T101 cross fractionating
apparatus produced by Dia Instrument Inc. is used. The cross
fractionating apparatus comprises an on-line combination of a
temperature rising elution fractionating (TREF) mechanism for
fractionating a specimen utilizing the difference of dissolution
temperature and a size exclusion chromatography (SEC) for further
fractionating the fractions by molecular size.
[0073] The sample to be measured (ethylene-.alpha.-olefin random
copolymer) is dissolved in a solvent (o-diclorobenzene) at a
temperature of 140.degree. C. to a concentration of 3 mg/ml. The
sample solution is then injected into a sample loop in the
measuring instrument. The following measurement is automatically
carried out under predetermined conditions. 0.4 ml of the sample
solution retained in the sample loop is then injected into a TREF
column (attached stainless steel column having an inner diameter of
4 mm and a length of 150 mm filled with glass beads as inert
carrier) for fractionating by the use of the difference of
dissolution temperature. Subsequently, the sample is cooled at a
rate of 1.degree. C. from 140.degree. C. to 0.degree. C. so that
the inert carrier is coated with the sample. In this manner, a
polymer layer is formed on the surface of the inert carrier
beginning with a high crystallizability component (easily
crystallized) and then with a low crystallizability component
(hardly crystallized). The TREF column is then held at a
temperature of 0.degree. C. for 30 minutes. 2 ml of the component
which is dissolved at a temperature of 0.degree. C. is then
injected into SEC columns (AD806MS, produced by Showa Denko K. K.;
three units are used) from the TREF column at a flow rate of 1
ml/minutes. While fractionating by molecular size is being effected
in SEC, the TREF column temperature is raised to the subsequent
elution temperature (5.degree. C.) where it is then kept for about
30 minutes. The measurement of fraction eluted at the various
temperatures in SEC is effected at a time interval of 39 minutes.
The elution temperature is raised stepwise as follows:
[0074] 0.degree. C., 5.degree. C., 10.degree. C., 15.degree. C.,
20.degree. C., 25.degree. C., 30.degree. C., 35.degree. C.,
40.degree. C., 45.degree. C., 49.degree. C., 52.degree. C.,
55.degree. C., 58.degree. C., 61.degree. C., 64.degree. C.,
67.degree. C., 70.degree. C., 73.degree. C., 76.degree. C.,
79.degree. C., 82.degree. C., 85.degree. C., 88.degree. C.,
91.degree. C., 94.degree. C., 97.degree. C., 100.degree. C.,
102.degree. C., 120.degree. C., 140.degree. C.
[0075] The solution fractionated by molecular size in SEC columns
is then measured for absorbance proportional to the polymer
concentration by an attached infrared spectrophotometer (detected
at a wavelength of 3.42 .mu.m with stretching vibration of
methylene) to obtain chromatogram of fractions eluted at the
various temperatures. Using a built-in data processing software,
the base line of chromatogram of fractions eluted at the various
temperatures is drawn. These data are then processed in operation.
The areas of these chromatograms are integrated to obtain
integrated elution curve. The integrated elution curve is then
differentiated by temperature to obtain differentiated elution
curve.
[0076] 2. Sample
[0077] (A) Ethylene Resin Constituting the Resin Layer
[0078] (1) Low Density Polyethylene (LDPE):
[0079] Novatech LD LC701, produced by Japan Polychem Corporation
(MFR: 14 g/10 minutes; density: 0.918 g/cm.sup.3)
[0080] (2) Ethylene-Vinyl Acetate Copolymer (EVA):
[0081] Novatech EVA LV260, produced by Japan Polychem Corporation
(MFR: 8.5 g/10 minutes; vinyl acetate content: 6.0%)
[0082] (3) Straight-Chain Low Density Polyethylene (LLDPE):
[0083] Novatech LL UC470, produced by Japan Polychem Corporation
(MFR: 12 g/10 minutes; density: 0.924 g/cm.sup.3)
[0084] (4) High Density Polyethylene (HDPE):
[0085] Novatech HD LY20, produced by Japan Polychem Corporation
(MFR: 8 g/10 minutes; density: 0.941 g/cm.sup.3)
[0086] (B) Straight-Chain Ethylene-.alpha.-Olefin Copolymer
[0087] (1) Synthesis of Ethylene-1-Hexene Copolymer (LLDPE-1)
[0088] To 2.0 mmol of ethylenebis(4,5,6,7-tetrahydroindenyl)
zirconium dichloride as a complex was then added methyl almoxane
produced by Toyo Stowfer Co., Ltd. in an amount of 1,000 mols per
mol of the catalyst. The mixture was then diluted with toluene to
make 10 1 to prepare a catalyst solution. The catalyst solution
thus obtained was then put into an agitated autoclave type
continuous reaction vessel having an inner capacity of 1.5 1. Into
the reaction vessel was then supplied a mixture of ethylene and
1-hexene in such an amount that the concentration of 1-hexene was
81% by weight The reaction mixture was then allowed to undergo
reaction at a temperature of 175.degree. C. while the pressure in
the reaction vessel was being kept at 2,200 kg/cm.sup.2 to obtain a
straight-chain ethylene-1-hexene copolymer (LLDPE-1) having MFR of
31 g/10 minutes, a density of 0.892 g/cm.sup.3 and a melting peak
temperature of 80.degree. C. which is eluted in an amount of 100%
at a temperature of 80.degree. C. or lower as determined by
temperature rising elution fractionating (TREF).
[0089] (2) Synthesis of Ethylene-1-Hexene Copolymer (LLDPE-2)
[0090] The catalyst solution used in the synthesis of LLDPE-1 was
put into an agitated autoclave type continuous reaction vessel
having an inner capacity of 1.5 1. Into the reaction vessel was
then supplied a mixture of ethylene and 1-hexene in such an amount
that the concentration of 1-hexene was 86% by weight. The reaction
mixture was then allowed to undergo reaction at a temperature of
150.degree. C. while the pressure in the reaction vessel was being
kept at 2,200 kg/cm.sup.2 to obtain a straight-chain
ethylene-l-hexene copolymer (LLDPE-2) having MFR of 9 g/10 minutes,
a density of 0.881 g/cm.sup.3 and a melting peak temperature of
60.degree. C. which is eluted in an amount of 100% at a temperature
of 80.degree. C. or lower as determined by temperature rising
elution fractionating (TREF).
EXAMPLES 1-2
[0091] (1) As the resin layer (A) there was used LDPE. As the resin
layer (B) there was used LLDPE-1 or LLDPE-2. The two resins were
each mixed thoroughly with 0.5% by weight of a phenolicstabilizerby
a blender. The two resins were each then melt-extruded so that they
were pelletized to form laminating resins.
[0092] (2) The foregoing laminating resins LDPE (A) and (B) were
then melt co-extruded through T-dies mounted on extruders having
bore diameters of 90 mm and 65 mm, respectively, at a resin
temperature of 250.degree. C. into films having a width of 500 mm
and a thickness of 10 .mu.m and 5 .mu.m, respectively, in such a
manner that the resin layer (A) is opposed to the substrate.
[0093] (3) Subsequently, a biaxially-stretched polypropylene film
(OPP) [LOF2 (trade name) produced by Hutamura Chemical Industries,
Ltd.] was discharged from the substrate delivery portion of the
extrusion lamination apparatus. The film was coated with an anchor
coat on one side thereof, and then dried. Ozone treatment was then
made on the interface of the coated surface of the stretched film
with the resin layer (A) which had been extruded in the form of
film together with the resin layer (B). The laminate was then
subjected to pressure lamination through the gap between a
surface-matted cooling roll and a compression rubber roll. The
laminate was then subjected to corona discharge treatment on the
surface of the resin layer (B) at 20W.min/m.sup.2 to obtain a
laminated film. The workability during the foregoing procedure and
the results of evaluation of laminated film are set forth in Table
1.
[0094] (4) Subsequently, the laminated film thus obtained and an
offset-printed art paper were subjected to thermocompression
bonding at a roll temperature of 70.degree. C., 80.degree. C. and
100.degree. C., a linear pressure of 55.6 kg and a rate of 30
m/min. in such an arrangement that the corona-discharged surface of
the laminated film was opposed to the art paper by a press to
obtain a thermal laminate.
[0095] (5) The results of evaluation of gloss of the thermal
laminate thus obtained, adhesive strength of the thermal laminate
to the printed art paper and tunneling of the thermal laminate with
respect to the printed art paper are set forth in Table 2.
EXAMPLE 3
[0096] A laminated film and a thermal laminate were prepared in the
same manner as in Example 1 except that as the resin layer (A) and
the resin layer (B) there were used EVA and LLDPE-1, respectively,
which were then melt co-extruded through T-dies mounted on
extruders having bore diameters of 90 mm and 65 mm, respectively,
at a resin temperature of 240.degree. C. into a film having a width
of 500 mm and a thickness of 10 .mu.m and 5 .mu.m, respectively, in
such an arrangement that the resin layer (A) is opposed to the
substrate. The results of evaluation of the laminated film and
thermal laminate are set forth in Tables 1 and 2.
EXAMPLE 4
[0097] A laminated film and a thermal laminate were prepared in the
same manner as in Example 1 except that as the resin layer (A) and
the resin layer (B) there were used LLDPE and LLDPE-1,
respectively, which were then melt co-extruded through T-dies
mounted on extruders having bore diameters of 90 mm and 65 mm,
respectively, at a resin temperature of 250.degree. C. into a film
having a width of 500 mm and a thickness of 10 .mu.m and 5 .mu.m,
respectively, in such an arrangement that the resin layer (A) is
opposed to the substrate. The results of evaluation of the
laminated film and thermal laminate are set forth in Tables 1 and
2.
EXAMPLE 5
[0098] A laminated film and a thermal laminate were prepared in the
same manner as in Example 1 except that as the resin layer (A) and
the resin layer (B) there were used HDPE and LLDPE-1, respectively,
which were then melt co-extruded through T-dies mounted on
extruders having bore diameters of 90 mm and 65 mm, respectively,
at a resin temperature of 250.degree. C. into a film having a width
of 500 mm and a thickness of 10 .mu.m and 5 .mu.m, respectively, in
such an arrangement that the resin layer (A) is opposed to the
substrate. The results of evaluation of the laminated film and
thermal laminate are set forth in Tables 1 and 2.
COMPARATIVE EXAMPLE 1
[0099] (1) LLDPE-1 was mixed thoroughly with 0.5% of a phenolic
stabilizer by a blender. The resin was then melt-extruded into
pellets to form a laminating resin.
[0100] (2) The foregoing laminating resin was then melt-extruded
through a T-die mounted on an extruder having a bore diameter of 90
mm at a resin temperature of 250.degree. C. into a film having a
width of 500 mm and a thickness of 15 .mu.m.
[0101] (3) A laminated film and a thermal laminate were then
prepared in the same manner as in Example 1. The results of
evaluation of the laminate film and thermal laminate are set forth
in Tables 1 and 2.
COMPARATIVE EXAMPLE 2
[0102] A laminated film and a thermal laminate were prepared in the
same manner as in Comparative Example 1 except that a resin
composition comprising 90% by weight of LLDPE-1 and 10% by weight
of LDPE was mixed thoroughly with 0.5% by weight of a phenolic
stabilizer by a blender, and then melt-extruded into pellets to
form a laminating resin. The results of evaluation of the laminated
film and the thermal laminate are set forth in Tables 1 and 2.
COMPARATIVE EXAMPLE 3
[0103] A laminated film and a thermal laminate were prepared in the
same manner as in Comparative Example 1 except that as the
laminating resin there was used an ethylene-vinyl acetate copolymer
(EVA, "Novatech EVA LV570", produced by Japan Polychem Corporation;
MFR: 15 g/10 min.; vinyl acetate content: 20% by weight) and the
melt extrusion temperature was changed to 240.degree. C. The
results of evaluation of the laminated film and the thermal
laminate are set forth in Tables 1 and 2.
1 TABLE 1 Adhesive layer resin Extrusion Total Laminated film
Substrate temperature Resin layer Resin layer thickness Blocking
(.mu.m) (.degree. C.) (A)/thickness (.mu.m) (B)/thickness (.mu.m)
(.mu.m) Workability resistance Example 1 OPP/15 250 LDPE/10
LLDPE-1/5 15 Good .circleincircle. 2 OPP/15 250 LDPE/10 LLDPE-2/5
15 Good .circleincircle. 3 OPP/15 240 EVA/10 LLDPE-1/5 15 Good
.circleincircle. 4 OPP/15 250 LLDPE/10 LLDPE-1/5 15 Good
.circleincircle. 5 OPP/15 250 HDPE/10 LLDPE-1/5 15 Good
.circleincircle. Comparative 1 OPP/15 250 LLDPE-1/15 LLDPE-1/5 15
Poor -- Example 2 OPP/15 250 LLDPE-1/90 WT-%; 15 Good
.circleincircle. LDPE/10 WT-%/15 3 OPP/15 240 EVA (LV570)/15 15
Good .largecircle.
[0104]
2TABLE 2 Properties to be evaluated Results of evaluation
Lamination Gloss Adhesive strength Elmendorf tear temperature %
Gloss Obscured image (g/25 mm) Tunneling strength (gf) (.degree.
C.) 70 80 100 70 80 100 70 80 100 70 80 100 MD TD Example 1 89 90
92 .largecircle. .largecircle. .largecircle. 550 870 1060
.circleincircle. .circleincircle. .circleincircle. 6.3 3.3 2 89 90
93 .largecircle. .largecircle. .largecircle. 760 1050 1130
.circleincircle. .circleincircle. .circleincircle. 6.5 3.7 3 89 91
95 .largecircle. .largecircle. .largecircle. 580 900 1080
.circleincircle. .circleincircle. .circleincircle. 6.8 4.0 4 89 91
93 .largecircle. .largecircle. .largecircle. 560 900 1100
.circleincircle. .circleincircle. .circleincircle. 5.8 3.0 5 89 92
95 .largecircle. .largecircle. .largecircle. 580 920 1150
.circleincircle. .circleincircle. .circleincircle. 5.5 2.8
Comparative 1 -- -- -- -- -- -- -- -- -- -- -- -- -- -- Example 2
70 88 90 X .DELTA. .largecircle. 100 250 450 X .largecircle.
.circleincircle. 10.8 7.6 3 65 80 88 X X .largecircle. 50 100 250 X
X .largecircle. 7.7 4.8
[0105] The film for thermal laminate according to the invention
comprises two adhesive resin layers laminated on a thermoplastic
resin film substrate. The resin (B) constituting the adhesive layer
which is heat-bonded to the printed surface of the printed matter
exhibits a melting peak temperature of as low as 102.degree. C. or
lower, preferably 92.degree. C. or lower, as determined by
differential scanning calorimetry (DSC). Thus, the film for thermal
laminate according to the invention can laminate the printed
surface of the printed matter at a low temperature. The resulting
thermal laminate can be prevented from undergoing discoloration of
printing ink and being curled. The laminated film has an improved
cuttability during print lamination. Further, by allowing the resin
layer (A) and the resin layer (B) to be co-extruded, surging can be
prevented during extrusion lamination, making it possible to effect
stabilized film formation.
[0106] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
* * * * *